how to create two columns based on a certain criterior from the original two column?

[where_pc]

Hi there ,

I may have a simple question, however it is difficult for me. If you can help, that would be great! there is two columns, lets say

0.1 3
0.2 10
0.3 8
0.4 41
0.5 16
0.6 19
0.7 21
0.8 15
0.9 17

I want to creat a new two columns partially from the original column based on the criterior, when A=0.1*N( N=3i) , choose B

0.1 3
0.3 8
0.6 19
0.9 17

I am not sure if I fully state it. Thanks !

Where_pc